Pintle for radial piston machines

ABSTRACT

A radial piston machine wherein the high-pressure control chamber of the pintle is located between two recesses and defines therewith two sealing projections of varying width, either because the width of the control chamber varies in the circumferential direction of the pintle or due to specific configuration of the recesses. This insures that the point of attack of the resultant force furnished by pressure fields which develop between the sealing projections and the internal surface of the rotating cylinder block as a result of leakage of pressurized fluid from the high-pressure control chamber coincides with or is immediately adjacent to the point of attack of the resultant of and neutralizes all forces which tend to move the cylinder block out of axial alignment with the pintle. The cylinder block tends to move out of axial alignment with the pintle due to fluid pressure in certain cylinders of the cylinder block and also due to the pressure which the pistons apply to the surfaces surrounding the respective cylinders.

United States Patent 91 Nonnenmacher Apr. 1, 1975 v PINTLE FOR RADIALPISTON MACHINES [75] Inventor: Gerhard Nonnenmacher,Korntal,

Germany [22] Filed: Sept. 28, 1973 [21] Appl. No.: 401,943

[30] Foreign Application Priority Data 796,163 1/1936 France 91/498Primary E.raminerWilliam lL. Freeh Attorney, Agent, or Firm-Michael S.Striker [57] ABSTRACT A radial piston machine wherein the high-pressurecontrol chamber of the pintle is located between two recesses anddefines therewith two sealing projections of varying width, eitherbecause the width of the control chamber varies in the circumferentialdirection of the pintle or due to specific configuration of therecesses. This insures that the point of attack of the resultant forcefurnished by pressure fields which develop between the sealingprojections and the internal surface of the rotating cylinder block as aresult of leakage of pressurized fluid from the high-pressure controlchamber coincides with or is immediately adjacent to the point of attackof the resultant of and neutralizes all forces which tend to move thecylinder block out of axial alignment with the pintle. The cylinderblock tends to move out of axial alignment with the pintle due to fluidpressure in certain cylinders of the cylinder block and also due to thepressure which the pistons apply to the surfaces surrounding therespective cylinders.

18 Claims, 13 Drawing Figures PINTLE FOR RADIAL PISTON MACHINESBACKGROUND OF THE INVENTION The present invention relates to radialpiston ma chines in general, and more particularly to improvements inradial piston machines wherein the position of a slide block withrespect to a stationary pintle determines the length of strokes of thepistons which are reciprocable in radially extending cylinders of apiston block which rotates about the pintle.

As a rule, the pintle (also called valve) is provided with at least twocontrol chambers which are located diametrically opposite each other andcommunicate with two axially extending bores of the pintle. The cylinderblock has an internal surface which rotates about the peripheral surfaceof the pintle and is provided with a series of ports, one for eachcylinder, which sweep seriatim past and communicate with the two controlchambers when the cylinder block rotates, either in response totransmission of torque from a prime mover or in response to admission ofpressurized fluid from one of the control chambers, i.e., depending uponwhether the machine is used as a pump or as a motor. It is already knownto provide the peripheral surface of the pintle with twocircumferentially extending recesses which flank the control chambersand define therewith a first pair of elongated sealing projections orribs which are adjacent to one of the control chambers and a second pairof sealing projections which are adjacent to the other control chamber.When the machine is in use, some pressurized fluid invariably leaks fromone of the control chambers (i.e., from the high-pressure chamber) andflows along the adjacent sealing projections toward the recesses whichcommunicate with the interior of the housing of the radial pistonmachine. Additional fluid leaks along the other pair of sealingprojections as well as along sealing rings or carrying rings which flankthe recesses in the peripheral surface of the pintle. The fluid whichleaks between the sealing projections and sealing elements on the onehand, and the internal surface of the cylinder block on the other hand,establishes pressure fields which oppose the movement of adjacentportions of the internal surface of the cylinder block toward theperipheral surface of the pintle. The pressure fields are morepronounced beween the internal surface of the cylinder block and thosesealing projections which are adjacent to the high-pressure controlchamber. The control chambers are separated from each other by platformsor lands which constitute non-recessed portions of the peripheralsurface of the pintle.

When the cylinder block rotates, certain cylinders contain highlypressurized fluid which applies to the surfaces surrounding therespective cylinders a force tending to move the cylinder block towardthe pintle. The point of attack of this force travels back and forthabout the center of the high-pressure control chamber in and counter tothe direction of rotation of the cylinder block. The extent of angulardisplacement of the point of attack of the just discussed force withrespect to the pintle depends on the number of cylinders in the cylinderblock, i.e., on the angle between the axes of neighboring pistons. Inaddition, the pistons apply to the surfaces surrounding the respectivecylinders a lateral force which tends to move the cylinder block towardthe pintle in the region of that land which is being bypassed bysuccessive pistons WhlCI'l assume their inner end positions at a minimumdistance from the axis of the pintle. The resultant of all forcesproduced by fluid pressure and by the pistons acts on the cylinder blockin the region between the aforementioned land and the center of thehigh-pressure control chamber. The point of attack of such resultantforce travels back and forth, i.e., it can move closer to the center ofthe high-pressure control chamber or closer to the land which is beingbypassed by successive pistons which assume their inner end positions.

German Offenlegungschrift No. 1,453,629 discloses a radial pistonmachine wherein the pintle is provided with two circumferentiallycomplete recesses or grooves which flank the control chambers. The fluidwhich leaks from the high-pressure control chamber toward the recessesestablishes very pronounced pressure fields between the internal surfaceof the cylinder block and those sealing projections which areimmediately adjacent to the high-pressure control chamber. The resultantforce which is produced by the pressure fields and opposes the movementof cylinder block toward the pintle acts upon the cylinder block at thecenter of the high-pressure control chamber so that such force cannotneutralize or balance the aforediscussed resultant force which isproduced by fluid pressure in the cylinders and by the pistons and tendsto move the cylinder block toward the peripheral surface of the pintle.In other words, such pressure fields cannot balance a force which tendsto move the cylinder block toward the pintle and Whose point of attacktravels back and forth between that land which is adjacent to pistonsassuming their inner end positions and the center of the high-pressurecontrol chamber. This is due to the fact that the width of sealingprojections which are adjacent to the high-pressure control chamber isconstant from end to end.

SUMMARY OF THE INVENTION An object of the invention is to provide anovel and improved radial piston machine wherein the cylinder block isautomatically centered on the pintle.

Another object of the invention is to provide a novel and improvedpintle for use in radial piston machines of the type wherein thecylinder block is acted upon by a force which tends to move it towardthe periphery of the pintle and whose point of attack travels back andforth, as considered in the direction of rotation of the cylinder block.

A further object of the invention is to provide a pintle for use inradial piston machines with novel and improved control chambers and/orrecesses which insure a complete or practically complete neutralizationof all forces tending to move the axis of the rotating cylinder blockout of exact alignment with the axis of the pintle.

An additional object of the invention is to provide a pintle whichinsures that all forces acting on the pintle and on the cylinder blockare fully balanced or neutralized, at least within each of a successionof unit lengths of time, to thus insure accurate, reliable and automaticcentering of the cylinder block on the pintle and to thereby preventuncontrolled and excessive leakage of pressurized fluid between theperipheral surface of the pintle and the internal surface of thecylinder block.

The invention is embodied in a radial piston machine wherein the widthof pronounced pressure fields between the peripheral surface of thepintle and the internal surface of the cylinder block varies in thecircumferential direction of the pintle in such a way that the point ofattack of the resultant force produced by the pressure fields andopposing the movement of the cylinder block out of axial alignment withthe pintle coincides with or is closely adjacent to the point of attackof the resultant force (produced by fluid pressure and by the pistons)which tends to move the cylinder block out of axial alignment with thepintle.

An important advantage of such configuration of the pronounced pressurefields is that it can be achieved at a reasonable cost, i.e., by thesimple expedient of properly configurating the peripheral surface of thepintle. The width of pronounced pressure fields can be varied byproperly selecting the configuration of recesses in the peripheralsurface of the pintle and/or by properly selecting the configuration ofone or both control chambers in the peripheral surface of the pintle.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved pintle itself, however, both as to its construction and itsmode of operation, together with additional features and advantagesthereof, will be best understood upon perusal of the following detaileddescription of certain specific embodiments with reference to theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is central vertical sectionalview of radial piston machine having a pintle which embodies one form ofthe invention;

FIG. 2 is a developed view of a portion of the pintle in the radialpiston machine of FIG. 1;

FIG. 3 is a developed view of a portion of a second pintle;

FIG. 4 is a developed view of a portion ofa third pintle;

FIG. 5 is a developed view of a portion of a fourth pintle;

FIG. 6 is a developed view of a portion of a fifth pintle;

FIG. 7 is a developed view of a portion of a sixth pin tle;

FIG. 8 is a developed view of a portion of a seventh pintle;

FIG. 9 is a developed view of a portion of a eighth pintle;

FIG. 10 is a developed view of a portion of a ninth pintle;

FIG. 11 is a developed view of a portion of a tenth pintle;

FIG. 12 is a developed view of a portion of an eleventh pintle; and

FIG. 13 is a transverse sectional view as seen in the direction ofarrows from the line XIIIXIII of FIG. 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a radialpiston machine including a housing 1 having a cover 2 which is providedwith a bore 3 for a stationary valve or pintle 4. The pintle 4 is heldagainst rotation by a pin 4a and is provided with two axial ports orbores 21, 22, communicating with two peripheral slots or controlchambers 19, best shown in FIG. 2. A cylinder block 5 rotates on thepintle 4 and in a friction bearing 6 which is installed in thehousing 1. The shaft 7 of the cylinder block 5 is driven by a primemover (not shown) when the machine is operated as a pump. The cylinderblock 5 rotates the shaft 7 when the machine is used as a motor. Thecylinder block 5 is formed with radially extending equidistant cylinders8 for pistons 9 which are received equidistant cylinders 8 for pistons 9which are received in the cylinders with minimal clearance and areprovided with articulately mounted shoes or heads 10 abutting againstthe internal surface of a slide block 1 1 which is adjustable radiallyof the pintle 4 to thereby determine the length of piston strokes. Thecontrol means for changing the position of the slide block 11 comprisesa nut 14 which is rigid with the slide block, a spindle 15 which mesheswith the nut 14 and is rotatable in but cannot move axially relative toa bracket 16 of the housing 1, and a handwheel 17 for the spindle 15. Ahelical spring 18 reacts against the housing 1 and bears against theslide block 11 diametrically opposite the nut 14.

Each cylinder 8 has a conical inner end portion 12 which tapers in adirection towrd the periphery of the pintle 4 and communicates with aport 13 of the cylinder block 5. When the cylinder block 5 rotates, theports 13 communicate seriatim with the control chamber 19, thereuponwith the control chamber 20, again with the control chamber 19, and soforth. The control chambers 19, 20 are elongated slots of constant width(see FIG. 2) which extend in the circumferential direction of the pintle4 in line with the ports 13 and pistons 9 in the cylinder block 5. Thecontrol chamber 19 is assumed to constitute a low-pressure chamber andthe control chamber 20 is assumed to constitute a highpressure chamber.Thus, when the radial piston machine of FIG. 1 is operated as a pump,pressurized fluid is forced from successive ports 13 into the chamber 20and the ports 13 thereupon draw fluid from the chamber 19.

As shown in FIG. 2, the control chambers 19, 20 are separated from eachother by two platforms or lands 23, 24. When the machine is operated asa pump, P cylinder block 5 is assumed to rotate in the directlonindicated by arrow A. The land 23 is adjacent to the ports 13 inregister with those pistons 9 which are located at a maximum distancefrom the pintle 4 and the land 24 is adjacent to those pistons 9 whichare nearest to the pintle. I

The control chambers 19, 20 are flanked by two C11- cumferentiallycomplete recesses or grooves 25 26 which are configurated in accordancewith a feature of the present invention. The width of each of therecesses 25, 26 is constant and these recesses are mirror symmetrical toeach other with reference to a plane wlnch is normal to the axis of thepintle 4 and halves the control chambers 19, 20 and lands 23, 24.

The recess 25 includes a portion 25a which is parallel to thelongitudinal direction of the control chamber 19 and is separated fromthis control chamber by an elongated sealing projection or rib 29 ofconstant width. At or close to the median portion of the land 23, therecess 25 includes a relatively short portion 25b which extends axiallyof the pintle 4 and toward the recess 26, and the portion 25b isfollowed by a portion 250 which is inclined away from the recess 26 anddefines with the control chamber 20 a sealing projection or rib 27having a width which increases in a direction from the land 23 towardthe land 24. At the middle of the land 24, the recess 25 includes afourth portion 25d which extends axially of the pintle 4 andcommunicates with the ad acent end of the portion a. the correspondingportions of the recess 26 are shown at 26a, 26b, 26c and 26d. Thesealing projections or ribs which the portions 26a and 26c define withthe control chambers 19 and 20 are respectively shown at and 28. It willbe seen that the sealing projections 29 and 30 are substantiallyrectangular and that the sealing projections 27, 28 have a triangular ortrapezoidal outline.

The recesses 25, 26 are respectively adjacent to two circumferentiallycomplete sealing or carrying elements in the form of rings 31, 32. Thesealing element 31 extends all the way to the inner axial end of thepintle 4.

When the radial piston machine is in use, pressurized fluid leaks fromthe control chamber 20 toward the recesses 25, 26 by flowing through thegap between the periphery of the pintle 4 and the internal surface ofthe cylinder block 5. The escaping fluid establishes pronounced pressurefields along the sealing projections 27, 28; such pressure fields opposethe movement of the adjacent portion of the cylinder block 5 toward theperiphery of the pintle 4. Due to the fact that the width of sealingprojections 27, 28 increases in a direction from the land 23 toward theland 24, the centers of the two pronounced pressure fields are shiftedin a direction from the center of the control chamber 20 toward the land24, i.e., toward the region where the pistons 9 travel when they reachthe inner ends of their strokes. The fluid also leaks from the recesses25, 26 and along the sealing elements 31, 32 to enter the interior ofthe housing 1. Moreover, and if the fluid pressure in the controlchamber 19 is less than the fluid pressure in the recesses 25, 26, thefluid also flows from the recesses 25, 26 toward the control chamber 19to establish less pronounced pressure fields between the sealingprojections 29, 30 and the internal surface of the cylinder block 5. Theability of these less pronounced pressure fields (as well as of the lesspronounced pressure fields between the sealing elements 31, 32 and theinternal surface of the cylinder block 5) to oppose the movement of thecorresponding portions of the cylinder block 5 toward the periphery ofthe pintle 4 is much less than that of more pronounced pressure fieldsin the region of the sealing projections 27, 28. The leakage of fluidfrom the recesses 25, 26 causes the fluid pressure in the recesses 25,26 to drop so that it matches the fluid pressure in the interior of thehousing 1 or in the control chamber 19, whichever pressure is lower. Theweaker or less pronounced pressure fields in the region of the sealingelements 31, 32 and sealing projections 29, 30 balance or compensateeach other, either completely or substantially, so that the point ofattack of the resultant of all forces produced by the pressure fieldscoincides with or is close to the common center of pronounced pressurefields in the region of the sealing projections 27, 28. Thus, byproperly selecting the configuration of recesses 25, 26 (and hence theconfiguration of sealing projections 27, 28), one can insure that theaforediscussed resultant force acting upon the cylinder block 5 andtending to move the axis of the cylinder block out of exact alignmentwith the axis of the pintle is balanced by the resultant of forcesproduced by pronounced pressure fields between the sealing projections27, 28 and the internal surface f the cylinder block 5.

The pintle 4 of FIGS. 1 and 2 is designed for use in radial pistonmachines wherein the control chamber 20 is always the high-pressurechamber, wherein the control chamber 19 is always the low-pressurechamber, and wherein the piston 9 are nearest to the pintle 4 whiletraveeling along the land 24.

The pintle 35 of FIG. 3 is similar to the pintle 4 and is also used inradial piston machines wherein one of the control chambers (the chamber36) is always the high-pressure chamber, the other control chamber (37)is always the low-pressure chamber, and the pistons of the cylinderblock (not shown) always travel along the land 39 while assuming theirinner end positions. The direction of rotation of the cylinder block(when the machine operates as a pump) is indicated by the arrow A. Thetwo lands are shown at 38, 39, the sealing projections which flank thecontrol chamber 36 at 44, 45, the sealing projections which flank thecontrol chamber 37 at 42, 43, the sealing elements at 46, 47 and thecircumferentially complete recesses at 40, 41.

The recesses 40, 41 are mirror symmetrical to each other with referenceto a plane which is normal to the axis of the pintle 35 and halves thecontrol chambers 36, 37 and lands 38, 39. The recess 40 comprises afirst portion 40a which extends from the center of the land 39 to thecenter of the land 38 and is parallel to the longitudinal extension ofthe control chamber 37, a short portion 40b which extends axially of thepintle 35 toward the recess 41, a third portion 400 which is parallel tothe portion 40a, a fourth portion 40d which extends axially of thepintle 35 and away from the recess 41 and is located substantiallymidway between the ends of the control chamber 36, a fifth portion 40awhich is parallel to the portion 40a and extends to the middle of theland 39, and a sixth portion 40f which extends axially of the pintle 35and communicates with the adjacent end of the portion 40a. Thecorresponding portions of the recess 41 are respectively shown at 41 a,41b, 41c, 41d, 41e and 41f. The length of the portions 40b, 40f issubstantially half the length of the portion 40d, i.e., the plane of theportion 400! is located substantially midway between the plane of theportion 40c and the plane of the portion 40c.

The width of sealing projections 42, 43 is constant from end to end. Thesealing projections 44, 45 have narrower portions which are adjacent tothe land 38 and wider portions which are adjacent to the land 39. Suchconfiguration of sealing projections 44, 45 insures that the commoncenter of pressure fields which develop between the sealing projections44, 45 and the internal surface of the cylinder block is shifted in adirection from the center of the high-pressure control chamber 36 towardthe land 3'9. This again insures that the forces which act on thecylinder block and tend to move its axis out of axact alignment with thepintle 35 are properly balanced by the force which is produced bypronounced pressure fields in the region of sealing projections 44, 45.The pintle of FIG. 4 is designed for use in a radial piston machinewherein each of the control chambers 53, 54 can constitute ahigh-pressure chamber or a low-pressure chamber but the direction ofeccentricity of the associated cylinder block (not shown) remainsunchanged. The double-headed arrow B indicates that the cylinder blockcan rotate in either direction. The control chambers 53, 54 areseparated from each other by platforms or lands 5], 52. lrrespective ofthe direction of rotation of the cylinder block, the land 51 is adjacentto those pistons which assume their outer end positions (at a maximumdistance from the pintle); the pistons are adjacent to the land 52 whenthey reach their inner end positions.

The peripheral surface of the pintle 50 is further provided with tworecesses 55, 56 each of which is a circumferentially complete groove.The recess 55 has a first portion 55a which is adjacent to the controlchamber 53 and is inclined toward the recess 56 all the way from thecenter of the land 52 toward the center of the land 51, and a secondportion 55b which is inclined in the opposite direction (away from therecess 56). The corresponding mirror symmetrical portions of the recess56 are shown at 560 and 56b. It will be noted that the distance betweenthe portions 55a, 56a increases in a direction from the land 51 towardthe land 52 and that the distance between the portions 55b, 56bdecreases in a direction from the land 52 toward the land 51. Thesealing projections which respectively flank the control chambers 53, 54are shown at 57, 58 and 59, 60. The recesses 55, 56 are inwardlyadjacent to two circumferentially complete sealing or carrying elements61, 62. Each of the sealing projections 57-60 has a substantiallytrapezoidal or triangular outline. The bgses of the projections 57-60are adjacent to the land If the control chamber 53 constitutes thehighpressure chamber, pressurized fluid leaks from the chamber 53 to therecesses 55, 56 and forms pronounced pressure fields along the sealingprojections 57, 58. The center of these pressure fields (which canfurnish a substantial resistance to movement of the adjacent portion ofthe cylinder block toward the periphery of the pintle 50) is shiftedfrom the center of the high-pressure chamber 53 toward the land 52. Thisland is adjacent to the pistons which assume their inner end positions.Fluid which penetrates into the recesses 55, 56 leaks along the sealingelements 61, 62 to establish relatively weak or less pronounced pressurefields. Further less pronounced pressure fields develop between thesealing projections 59, 60 and the internal surface of the cylinderblock if the pressure in the chamber 54 is lower than in the recesses55, 56. The forces produced by all these relatively weak pressure fieldsare in a state of substantial or exact equilibrium so that the center ofthe resultant force produced by all pressure fields is only slightly outof line with the resultant force produced by pronounced pressure fieldsin the region of the sealing projections 57 and 58. The point of attackof the averaged force acting on the pintle 50 is practically identicalwith the point of attack of the resultant of forces produced by allpressure fields. These two forces are identical or nearly identical.

The situation is analogous when the control chamber 54 constitutes thehigh pressure chamber. The pronounced pressure fields then develop inthe region of sealing projections 59, 60 and their centers are shiftedfrom the center of the control chamber 54 toward the land 52. It will benoted that the forces are in virtual or exact equilibrium irrespectiveof the direction of rotation of the cylinder block.

The pintle 65 of FIG. 5 serves the same purpose as the pintle 50 of FIG.4, i.e., each of its control chambers 68, 69 may constitute thehigh-pressure chamber or the low-pressure chamber. The control chambers68, 69 are separated from each other by platforms or lands 66, 67. Thepistons which reach the outer ends of their strokes travel past the land66, and the pistons which reach the inner ends of their strokes (nearestto the pintle 65) travel past the land 67. The two endless recesses 70,71 are similar to the recesses 55, 56 except that they do not consist ofmutually inclined straight portions but rather of arcuate portionshaving concave sides facing the land 67, convex sides facing the land66, and nearly straight intermediate portions which are inclined withrespect to each other and flank the seal ing projections 72, 73 and 74,75 which are respectively adjacent to the control chambers 68 and 69.The recess 70 comprises a first arcuate portion 70a which forms part ofthe circle having its center above the pintle 65, as viewed in FIG. 5,and extending from the center of the chamber 68 to the center of thechamber 69, and a second arcuate portion 7012 which also forms part of acircle having its center of curvature at a level below the pintle 65, asviewed in FIG. 5. The corresponding portions of the recess 71 arerespectively shown at 71a and 71b. The distance between the recesses 70,71 is smallest in the region of the land 66 and greatest in the regionof the land 67. Thus, the width of the sealing projections 72, 73 aswell as 74, 75 increases in a direction from the land 66 toward the land67. The two endless elements or rings are shown at 76 and 77; theserings are respectively adjacent to the recesses 70, 71.

The manner in which the pressure fields develop when the cylinder blockrotates in a clockwise or counterclockwise direction is the same asdescribed in connection with FIG. 4.

If desired, the recesses 70 and 71 can be modified so that they consistof portions which resemble sinusoidal curves instead of portions ofcircles. The configuration of such sinusoidal recesses deviates rathernegligibly from the configuration of the recesses 70, 71 and thefunction of a pintle having such sinusoidal recesses is practicallyidentical to that of the pintle 50.

FIG. 6 illustrates a further pintle 80 which is analogous to the pintle50 of FIG. 4. Each of the two control chambers 83, 84 which areseparated from each other by platforms or lands 81, 82 may constitute ahighpressure chamber or a low-pressure chamber. The cylinder block (notshown) can rotate clockwise or counterclockwise (see the arrow B) andthe pistons which are nearest to the pintle 80 travel past the land 82.

The peripheral surface of the pintle 80 is provided with two endlessmirror symmetrical recesses 85, 86 which are respectively adjacent toendless sealing elements or rings 91, 92 and respectively define withthe control chambers 83, 84 pairs of sealing projections or ribs 87, 88and 90, 89. The recess 85 comprises portions 85a, 85c which extend inthe circumferential di rection of the pintle 80 and portions 85b, 85dwhich extend in parallelism with the axis of the pintle. Thecorresponding portions of the recess 86 are shown at 86a 86c and 86b,86d. The distance between the portions 85a, 86a is less than thedistance between the portions 850, 86c and each of these portionsextends from the center of the control chamber 83 to the center of thecontrol chamber 84. It will be seen that each of the sealing projections87-90 comprises a narrower portion of constant width which is nearer tothe land 81 and a wider portion of constant width which is nearer to theland 82. The width of the sealing projections 87, 88 increases abruptlysubstantially midway between the ends of the control chamber 83, and thewidth of the sealing projections 89, 90 increases abruptly midwaybetween the ends of the control chamber 84.

The centers of high pressure fields in the region of those sealingprojections which flank the high-pressure control chamber are shiftedfrom the center of the high-pressure control chamber toward the land 82.The manner in which pressure fields develop in the region of the sealingprojections, lands and sealing elements is analogous to that describedin connection with FIGS. 4 to 6.

The pintle 95 of FIG. 7 is analogous to the pintle of FIG. 4, i.e., eachof its control chambers 98, 99 can constitute a high-pressure chamber ora low-pressure chamber. The lands are shown at 96, 97, the ringshapedsealing elements at 106, 107, the sealing projections flanking thecontrol chamber 98 at 102, 103, the sealing projections flanking thecontrol chamber 99 at 104, 105, and the two endless recesses at 100,101. When the radial piston machine embodying the pintle 95 is in use,the pistons reach their inner end positions (nearest to the peripheralsurface of the pintle) while travelling along the land 97. The land 96is located dia metrically opposite the land 97 and is approached bysuccessive pistons which assume their outer end positions.

The recess 100 comprises a first portion 100a which is adjacent to theland 96 and is located in a plane which is exactly normal to the axis ofthe pintle 95, a second portion which is adjacent to the control chamber98 and is inclined away from the recess 101, a third portion 1006 whichis parallel to the portion 100a and is adjacent to the land 97, and afourth portion 100d which is inclined away from the recess 101. Thecorresponding portions of the recess 101 are shown at 101a, 101b, 1016and 10111. It will be noted that the distance between the portions 100a,101a, as considered in the axial direction of the pintle 95, is lessthan the distance between the portions 100C, 1016. The width of each ofthe four sealing projections 102-105, as considered in the axialdirection of the pintle 95, increases continuously in a direction fromthe land 96 toward the land 97. Each ofthese projections has atrapezoidal outline, and the base of each projection is adjacent to theland 97.

When the cylinder block (not shown) rotates clockwise orcounterclockwise (see the double-headed arrow B), the point of attack ofthe resultant force produced by all pressure fields between theperipheral surface of the pintle 95 and the cylinder block coincideswith or is closely adjacent to the point of attack of the resultantforce which urges the cylinder block toward the peripheral surface ofthe pintle. The pronounced pressure fields develop in the region ofthose sealing projections which flank the high-pressure control chamber.The point of attack of the resultant force produced by such pronouncedpressure fields is located between the center of the high-pressurecontrol chamber and the land 97.

The pintle 110 of FIG. 8 is intended to be used in a radial pistonmachine wherein the cylinder block invariably rotates in the directionindicated by the arrow A but the eccentricity of the slide block canchange from one side to the other side of the pintle 110. The peripheralsurface of the pintle 110 is provided with two elongated controlchambers 113, 114 of constant width, as considered in the axialdirection of the pintle. These control chambers are separated from eachother by two platforms or lands 111, 112. The land 111 is adjacent tothose pistons which dwell in their inner end positions when the axis ofthe slide block is located above the axis of the pintle (as viewed inFIG. 1) and the land 112 is adjacent to such pistons when the axis ofthe slide block is located at the opposite side of the axis of thepintle. It is assumed that the machine embodying the pintle is used as apump.

The peripheral surface of the pintle 110 is further provided with twoendless recesses 115, 116 which respectively define with the controlchambers 113, 114 pairs of sealing projections 117, 118 and 119, 120.Each of these projections is a trapezoid; the bases of the projections117, 118 are adjacent to the land 111 and the bases of the projections119, 120 are adjacent to the land 112. The recess 1115 has a firstportion 115a which is adjacent to the control chamber 114 and divergesfrom the corresponding first portion 11611 of the recess 116 in thedirection indicated by arrow A, i.e., from the land 111 toward the land112. A second portion 115b of the recess 111 extends axially of thepintle 110 toward the corresponding portion l16b of the recess 116, athird portion 11.50 of the recess 115 diverges from the correspondingportion 1166 of the recess 116, again in the direction indicated by thearrow A, and a fourth portion 115d of the recess 115 extends axially ofthe pintle 110 toward the corresponding portion 116d of the recess 116.The portions 116b, 1161) are aligned with the center of the land 112,and the portions 115d, 116d are aligned with the center of the land 111.The two endless sealing elements or rings are shown at 121 and 122.

The distance between the portions 115b, 116b, as considered in the axialdirection of the pintle 110, equals or closely approximates the distancebetween the portions 115d, 116a. The length of each of the portions115b, 115d, 116b, 116d is the same. It will be noted that the width ofeach of the four sealing projections 117-120, as considered in the axialdirection of the pintle 110, increases in the direction indicated by thearrow A.

If the control chamber 114 constitutes the highpressure chamber, and ifsuccessive pistons travel along the land 112 while such pistons assumetheir inner end positions, the operation of the: machine embodying thepintle 110 is analogous to that of the machine shown in FIG. 1 (i.e., ofthe machine embodying the pintle 4 of FIG. 2). A difference between thepintles 4 and 110 is that the width of sealing projections 29, 30 on thepintle 4 is constant and that the recesses 115, 116 diverge from eachother adjacent to each of the two control chambers 113, 114. Thisinsures that the forces acting on the pintle 110 are balanced by forcesacting on the cylinder block if the eccentricity of the slide block ischanged to such an extent that the pistons which are nearest to theperipheral surface of the pintle 110 travel along the land 111 (whilethe cylinder block continues to rotate in the direction indicated byarrow A).

The pintle 125 of FIG. 9 can be used for the same purpose as the pintle110 of FIG. 8, i.e., the axis of the slide block can be shifted from.the one to the other side of the pintle axis but the direction ofrotation of the cylinder block (arrow A) remains unchanged. The controlchambers 128, 129 have a constant width, as considered in theaxial'direction of the pintle 125, and are separated from each other byplatforms or land 126, 127. The pistons which assume their inner endpositions travel past the land 126 when the axis of the slide block islocated at one side of the axis of the pintle 125, and such pistonstravel past the land 127 when the axis of the slide block is located atthe other side of the axis of the pintle.

The peripheral surface of the pintle 125 is further provided with twoendless recesses 130, 131 which are flanked by circumferentiallycomplete sealing elements or rings 136, 137 and respectively define withthe control chambers 128, 129 pairs of sealing projections or ribs 132,133 and 134,135. The recess 130 includes portions 130a, 130b, 1306, 130dwhich are normal to the axis of the pintle 125 and portions 130e, 130f,130g, 13011 which are parallel to the axis of the pintle. Thecorresponding portions of the recess 131 are shown at131a,131b,l31c,131d, 131e, l31f, 131g and 13111. The portions 130a, 130b, 131a, l3lbare respectively coplanar with the portions 1300, 130d, 1310, 131d, andthe distance between the portions 130b, 131b and 130d, 131d exceeds thedistance between the portions 130a, 131a and 1300, 131e, as consideredin the axial direction of the pintle. The portions 130e, 1316 arealigned with the center of the land 126; the portions 130g, 131g arealigned with the center of the land 127; the portions 13012, 13111 arealigned with the center of the control chamber 128; and the portions130f, 131f are aligned with the center of the control chamber 129. Thewidth of each of the sealing projections 132135 increases stepwise inthe region of the center of the respective control chamber. The widerportions of the sealing projections 132, 133 are adjacent to the land126, and the wider portions of the sealing projections 134, 135 areadjacent to the land 127.

If the control chamber 129 is the high-pressure chamber and if thepistons which reach their inner end positions travel past the land 127,the manner in which the forces acting on the pintle 125 and on thecylinder block balance each other is analogous to that described inconnection with FIGS. 1-2 and 3. The difference is that theconfiguration of the sealing projections 132, I33 is identical with thatof the sealing projections 134, 135. Consequently, when the axis of theslide block is moved to the other side of the axis of the pintle 125,i.e., when the pistons which reach their inner end positions travel pastthe land 126, the forces acting on the pintle 125 and on the cylinderblock balance or neutralize each other in the same way as when thepistons which reach their inner end positions travel past the land 127.

The pintle 140 of FIG. has a control chamber 143 of constant width, asconsidered in the axial direction of the pintle, and a control chamber144 whose width increases in a direction from the land 141 toward theland 142. This pintle 140 is designed for use in a radial piston machinewherein the control chamber 144 always constitutes the high-pressurechamber and the pistons which reach their inner end positions invariablytravel past the land 142. The recesses 145, 146 are circumferentiallycomplete grooves each of which is located in a plane extending at rightangles to the axis of the pintle 140. The direction in which thecylinder block rotates is indicated by the arrow A, the two endlesssealing elements or rings are shown at 151, 152, the sealing projectionsor ribs which flank the low-pressure control chamber 143 are shown at147, 148, and the two sealing projections or ribs which flank thehighpressure control chamber 144 are shown at 149, 150.

The width of the sealing projections 147, 148, as considered in theaxial direction of the pintle 140, is constant. The width of the sealingprojections 149, 150 increases in a direction from the land 142 towardthe land 141. The width of each of the sealing elements 151, 152 isconstant.

That portion of the cylinder block which is adjacent to thehigh-pressure control chamber 144 is acted upon by a resultant forcewhich point of attack is located between the center of the controlchamber 144 and the land 142. Pressurized fluid leaks primarily from thecontrol chamber 144, along the sealing projections 149, 150, and intothe adjacent portions of the recesses 145, 146. Such fluid establishespronounced pressure fields which resist a movement of the cylinder blocktoward the control chamber 144. Additional fluid leaks along the sealingprojections 147, 148 and along the sealing elements 151, 152 (whence itenters the interior of the housing of the radial piston machine). Theforces which are produced by the less pronounced pressure fields in theregion of the sealing projections 147, 148 and sealing elements 151, 152neutralize each other and the point of attack ofthe resultant force withwhich the pronounced pressure fields in the region of the sealingprojections 149, 150 resist the approach of the cylinder block towardthe high-pressure control chamber 144 coincides with or is immediatelyadjacent to the point of attack of the force which tends to move thecylinder block toward the control chamber 144. By suitably configuratingand dimensioning the highpressure control chamber 144, one can insurethat the cylinder block is invariably centered on the pintle 1.40. Suchcentering can be achieved at a relatively low cost, i.e., by providingthe peripheral surface of the pintle 140 with two parallel recesses 145,146 of constant width and by machining the control chamber 144 in such away that its width increases gradually from the land 141 toward the land142.

The pintle 155 of FIG. 11 is similar to the pintle 140 of FIG. 10. Theonly difference is that the width of the high-pressure control chamber156 increases stepwise in a direction from the land 141 toward the land142. The sealing projections which flank the control chamber 156 areshown at 157 and 158; the width of each of these projections increasesstepwise in a direction from the land 142 toward the land 141. All otherparts of the pintle 155 are denoted by characters identical with thoseemployed in FIG. 10. It will be noted that the width of the right-handportion of the control chamber 156 substantially exceeds the width ofthe left-hand portion, and that the width of each of these portions isconstant. The abrupt increase in width of the control chamber 156 takesplace substantially or exactly midway between the lands 141 and 142.

The manner in which the forces acting on the pintle 155 are balanced byforces acting on the cylinder block is identical with the mannerdescribed in connection with the pintle 140 of FIG. 10.

Referring finally to FIGS. 12 and 13, there is shown a pintle 160 whichis similar to the pintle 4 of FIG. 2 except that its peripheral surfaceis formed with two recesses 225, 225 of finite length. It will be notedthat the recesses 225, 226 are interrupted in the region of the land 23.Furthermore, the recess 225 has a first portion 161 which diverges fromthe corresponding portion 162 of the recess 226 in a direction from theland 23 toward the land 24, a second portion 163 which is parallel tothe corresponding portion 164 of the recess 226, and a third orintermediate portion 165 which diverges from the corresponding portion166 of the recess 226 in a direction from the control chamber 19 towardthe control chamber 20. The portions 165, 166 are channels which aremachined into the body of the pintle 160 in the region of the land 24.As shown in FIG. 13, the ends of the channel 165 communicate withintermediate parts of the adjacent portions 161, 163 of the recess 225.Analogously, the ends of the channel 166 communicate with intermediateparts of the portions 162, 164 of the recess 226. The width of thesealing projections 29, 30, as considered in the axial direction of thepintle 160, is constant all the way from the land 23 to the land 24. Thewidth of the sealing projections 27, 28 increases continuously from theland 23 toward the land 24.

The channels 165, 166 insure that the fluid pressure in the portions161, 162 of the recesses 225, 226 re spectively equals the fluidpressure in the portions 163, 164. The two circumferentially completesealing elements or rings are shown at 167 and 168.

The operation of the radial piston machine which embodies the pintle 160is identical or analogous to that of the machine embodying the structureof FIGS. 1 and 2.

The pintles of FIGS. 3 to 9 can be modified by replacing theircircumferentially complete recesses with recesses which consist ofspaced-apart portions adjacent to the two control chambers or byreplacing the circumferentially complete recesses with recesses offinite length (see FIGS. 12 and 13). Each recess may com prise twoportions in the form of grooves and one or two portions in the form ofchannels. Referring to FIG. 7, the portions 100a, 1006, and 101a, 1016may constitute channels and the portions 100b, 100d, 101b, 101:! mayconstitute grooves. The channels bring about an equalization offluidpressure in the respective grooves. Referring again to FIG. 7, therecesses 100, 101 can be replaced by recesses of finite length whereinthe portions 100a, 101a are omitted, the portions 100b, 100d, 101b, 101dconstitute grooves, and the portions 100C, 1016 constitute channels.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of my contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

1. In a radial piston machine wherein a cylinder block having aplurality of radial cylinders for reciprocable fluid-pressurizingpistons rotates about a stationary pintle whose peripheral surface hashighand low-pressure control chambers located substantiallydiametrically opposite and separated from each other by first and secondlands one of which is adjacent to pistons assuming their inner endpositions, wherein successive cylinders communicate alternately withsaid highand lowpressure chambers when said cylinder block rotates.wherein said peripheral surface has only two circumferentially extendingendless recesses flanking said control chambers and respectivelydefining therewith a pair of first and a pair of second sealingprojections which are respectively adjacent to said highand low-pressurechambers, and wherein the fluid and the pistons in said cylindersproduce a first resultant force acting upon and tending to move saidcylinder block toward said pintle in the region between said one landand the center of said high-pressure chamber, the improvement whichconsists in that the width of said first sealing projections, asconsidered in the axial direction of said pintle, varies in thecircumferential direction of said peripheral surface and the fluid whchleaks from said high-pressure chamber substantially axially of thepintle toward said recesses produces pronounced pressure fields betweensaid first sealing projections and said cylinder block whereby saidpronounced pressure fields resist the movement of said cylinder blocktoward said pintle with a second resultant force, the point of attack ofsaid second resultant force coinciding with or being closely adjacent tothe point of attack of said first resultant force as a result ofvariation of the width of said first sealing projections.

2. The improvement as defined in claim 1, wherein each of said sealingprojections has a narrower first portion of constant width adjacent toone-half of the respective control chamber and a wider second portion ofconstant width adjacent to the other half of the respective controlchamber, the narrower portion of each first sealing projection beingadjacent to the wider portion of a second sealing projection and viceversa.

3. The improvement as defined in claim 1 wherein the width of saidcontrol chambers, as considered in the axial direction of said pintle,is constant in the circumferential direction of said peripheral surface.

4. The improvement as defined in claim 1, wherein the width of saidfirst sealing projections increases constantly from the other of saidlands toward said one land, as considered in the direction of rotationof said cylinder block, and wherein the width of said second sealingprojections is constant.

5. The improvement as defined in claim 1, wherein said recesses arelocated in parallel planes which are normal to the axis of said pintle.

6. The improvement as defined in claim 5, wherein the width of saidhigh-pressure control chamber increases continuously toward said oneland.

7. The improvement as defined in claim 5, wherein the width of saidhigh-pressure control chamber increases stepwise toward said one land.

8. The improvement as defined in claim 1, wherein the width of saidfirst sealing projections increases stepwise from the other of saidlands toward said one land, as considered in the direction of rotationof said cylinder block.

9. The improvement as defined in claim 8, wherein each of said firstsealing projections has a narrower portion of a first constant widthadjacent to one half of said high pressure chamber and a wider portionof a second constant width which is adjacent to the other half of saidsecond pressure chamber, and wherein each of said second sealingprojections has a constant width which is less than said second constantwidth but exceeds said first constant width.

10. The improvement as defined in claim 1, wherein the width of each ofsaid sealing projections increases in a direction from the other of saidlands toward said one land.

11. The improvement as defined in claim 10, wherein the distance betweensaid recesses, as considered in the axial direction of said pintle,increases continuously from the central portion of said other land tothe central portion of said one land.

12. The improvement as defined in claim 10, wherein each of saidrecesses includes a plurality of arcuate portions each forming part of acircle, the arcuate portions of each of said recesses including a firstarcuate portion having a concave side adjacent to said one land and asecond arcuate portion having a convex side adjacent to the other ofsaid lands, and wherein each of said sealing projections has asubstantially trapezoidal outline.

13. The improvement as defined in claim 10, wherein each of saidrecesses has a first portion adjacent to said one land, a second portionadjacent to the other of said lands, a third portion adjacent to one ofsaid control chambers, and a fourth portion adjacent to the other ofsaid control chambers, said first and second portions of said recessesbeing respectively parallel to each other, said third portions divergingfrom each other in a direction from said first towards said secondportions, and said fourth portions converging towards each other in adirection from said second towards said first portions, and wherein thedistance between said first portions, as considered in the axialdirection of said pintle, exceeds the distance between said secondportions.

14. The improvement as defined in claim 10, wherein each of saidrecesses includes a plurality of sinusoidal portions including a firstportion having a concave side adjacent to said one land and a secondportion having a convex side adjacent to the other of said lands, eachof said sealing projections having a substantially trapezoidal outline.

15. The improvement as defined in claim 10, wherein the width of each ofsaid sealing projections increases stepwise.

16. The improvement as defined in claim 15, wherein each of said sealingprojections comprises a relatively wide portion of a first constantwidth extending from said one land to the center of the respectivecontrol chamber and a relatively narrow portion of a second constantwidth extending from the center of the respective control chamber to theother of said lands.

17. The improvement as defined in claim 10, wherein the width of each ofsaid sealing projections increases continuously as considered in thedirection of rotation of said cylinder block.

18. The improvements as defined in claim 17, wherein each of saidrecesses comprises first and second portions which extend axially ofsaid pintle and are respectively aligned with the center of said oneland and with the center of the other of said lands, each of saidrecesses further comprising a third portion adjacent to one of saidchambers and diverging from the third portion of the other recess, and afourth portion adjacent to the other chamber and diverging from thefourth portion of the other recess.

1. In a radial piston machine wherein a cylinder block having aplurality of radial cylinders for reciprocable fluid-pressurizingpistons rotates about a stationary pintle whose peripheral surface hashigh- and low-pressure control chambers located substantiallydiametrically opposite and separated from each other by first and secondlands one of which is adjacent to pistons assuming their inner endpositions, wherein successive cylinders communicate alternately withsaid high- and lowpressure chambers when said cylinder block rotates.wherein said peripheral surface has only two circumferentially extendingendless recesses flanking said control chambers and respectivelydefining therewith a pair of first and a pair of second sealingprojections which are respectively adjacent to said high- andlow-pressure chambers, and wherein the fluid and the pistons in saidcylinders produce a first resultant force acting upon and tending tomove said cylinder block toward said pintle in the region between saidone land and the center of said high-pressure cHamber, the improvementwhich consists in that the width of said first sealing projections, asconsidered in the axial direction of said pintle, varies in thecircumferential direction of said peripheral surface and the fluid whchleaks from said highpressure chamber substantially axially of the pintletoward said recesses produces pronounced pressure fields between saidfirst sealing projections and said cylinder block whereby saidpronounced pressure fields resist the movement of said cylinder blocktoward said pintle with a second resultant force, the point of attack ofsaid second resultant force coinciding with or being closely adjacent tothe point of attack of said first resultant force as a result ofvariation of the width of said first sealing projections.
 2. Theimprovement as defined in claim 1, wherein each of said sealingprojections has a narrower first portion of constant width adjacent toone-half of the respective control chamber and a wider second portion ofconstant width adjacent to the other half of the respective controlchamber, the narrower portion of each first sealing projection beingadjacent to the wider portion of a second sealing projection and viceversa.
 3. The improvement as defined in claim 1 wherein the width ofsaid control chambers, as considered in the axial direction of saidpintle, is constant in the circumferential direction of said peripheralsurface.
 4. The improvement as defined in claim 1, wherein the width ofsaid first sealing projections increases constantly from the other ofsaid lands toward said one land, as considered in the direction ofrotation of said cylinder block, and wherein the width of said secondsealing projections is constant.
 5. The improvement as defined in claim1, wherein said recesses are located in parallel planes which are normalto the axis of said pintle.
 6. The improvement as defined in claim 5,wherein the width of said high-pressure control chamber increasescontinuously toward said one land.
 7. The improvement as defined inclaim 5, wherein the width of said high-pressure control chamberincreases stepwise toward said one land.
 8. The improvement as definedin claim 1, wherein the width of said first sealing projectionsincreases stepwise from the other of said lands toward said one land, asconsidered in the direction of rotation of said cylinder block.
 9. Theimprovement as defined in claim 8, wherein each of said first sealingprojections has a narrower portion of a first constant width adjacent toone half of said high pressure chamber and a wider portion of a secondconstant width which is adjacent to the other half of said secondpressure chamber, and wherein each of said second sealing projectionshas a constant width which is less than said second constant width butexceeds said first constant width.
 10. The improvement as defined inclaim 1, wherein the width of each of said sealing projections increasesin a direction from the other of said lands toward said one land. 11.The improvement as defined in claim 10, wherein the distance betweensaid recesses, as considered in the axial direction of said pintle,increases continuously from the central portion of said other land tothe central portion of said one land.
 12. The improvement as defined inclaim 10, wherein each of said recesses includes a plurality of arcuateportions each forming part of a circle, the arcuate portions of each ofsaid recesses including a first arcuate portion having a concave sideadjacent to said one land and a second arcuate portion having a convexside adjacent to the other of said lands, and wherein each of saidsealing projections has a substantially trapezoidal outline.
 13. Theimprovement as defined in claim 10, wherein each of said recesses has afirst portion adjacent to said one land, a second portion adjacent tothe other of said lands, a third portion adjacent to one of said controlchambers, and a fourth portion adjacent to the othEr of said controlchambers, said first and second portions of said recesses beingrespectively parallel to each other, said third portions diverging fromeach other in a direction from said first towards said second portions,and said fourth portions converging towards each other in a directionfrom said second towards said first portions, and wherein the distancebetween said first portions, as considered in the axial direction ofsaid pintle, exceeds the distance between said second portions.
 14. Theimprovement as defined in claim 10, wherein each of said recessesincludes a plurality of sinusoidal portions including a first portionhaving a concave side adjacent to said one land and a second portionhaving a convex side adjacent to the other of said lands, each of saidsealing projections having a substantially trapezoidal outline.
 15. Theimprovement as defined in claim 10, wherein the width of each of saidsealing projections increases stepwise.
 16. The improvement as definedin claim 15, wherein each of said sealing projections comprises arelatively wide portion of a first constant width extending from saidone land to the center of the respective control chamber and arelatively narrow portion of a second constant width extending from thecenter of the respective control chamber to the other of said lands. 17.The improvement as defined in claim 10, wherein the width of each ofsaid sealing projections increases continuously as considered in thedirection of rotation of said cylinder block.
 18. The improvements asdefined in claim 17, wherein each of said recesses comprises first andsecond portions which extend axially of said pintle and are respectivelyaligned with the center of said one land and with the center of theother of said lands, each of said recesses further comprising a thirdportion adjacent to one of said chambers and diverging from the thirdportion of the other recess, and a fourth portion adjacent to the otherchamber and diverging from the fourth portion of the other recess.